In an effort to make database management systems more scalable, multiple server processes can be clustered in such a way that together they function as a single logical system. Databases may be hosted on multiple nodes (servers), each of which hosts zero or more segments of the database. To distribute the data, an object (e.g. table or an index on the table) can be logically sub-divided into data segments. Physical manifestation of a data segment is called a clone. Thus, by dividing an entity (e.g. table, index) into one or more logical data segments and distributing the data corresponding to the logical segments (clones) across various nodes, scalability for the system can be achieved. While doing so, in order to make the data highly available and the system as a whole more fault-tolerant, multiple redundant copies of the data (multiple clones for each data segment) may be maintained. When nodes move between online and offline states due to failure or intentional administrative purposes, these clones can become stale due to updates that occur while the clones are offline (inaccessible).
Disaster Recovery (DR) is a key requirement for enterprise-class database systems. Facilitating disaster recovery typically involves maintaining up-to-date copies of databases at multiple locations that are separated geographically. One rudimentary approach to replicate a database distributed on multiple nodes to a remote site is to shutdown the database and copy data associated with the database onto the remote site, thereby making more efficient and effective techniques for disaster recovery desirable. Although this technique is able to provide a consistent image of the database to the remote site, it involves database downtime. Depending on the size of the database, this process is time consuming, inefficient, resource intensive, and incurs data loss most of the time. Moreover, taking a database offline, even for short periods of time, can be prohibitively costly and problematic. Thus, more effective and efficient replication strategies are desired for disaster recovery.